Amazon's numbers are still small compared to Netflix and YouTube, which continue to account for half of all broadband usage. But it does seem as though Bezos, who is spending billions to build up a video library that can compete with Netflix, is starting to make some headway.
Bezos insists he's not trying to compete with Netflix, even though the two companies do indeed compete for talent and licensing deals. But he has suggested that video could eventually become a "fourth pillar" of his company's business.
Netflix, meanwhile, is down nearly 2 percent from Sandvine's most recent measurement, last fall.
But Sandvine thinks that doesn't mean Netflix's consumer usage is down — which makes sense, since Amazon's subscriber numbers have continued to increase. Instead, it attributes the drop to a technique Netflix started using this year to optimize the amount of data it uses to stream a movie or a show, in hopes of cutting its bandwidth usage by 20 percent.
—By Peter Kafka, Recode.net.
CNBC's parent NBCUniversal is an investor in Recode's parent Vox, and the companies have a content-sharing arrangement.